The present invention relates to an inflatable Vehicle passenger restraint system that restrains an occupant during the critical period of an impact. More particularly, the present invention relates to such a system incorporating dual air bags arranged such that an inner air bag is located substantially within an outer air bag.
Inflatable restraint systems have become commonplace for passenger protection. Current federal regulations require all automobiles manufactured within the United States to be equipped with a passive restraint system, either an inflatable restraint system such as an air bag or a passive seat belt.
A typical inflatable restraint system includes three basic components: a crash sensing mechanism which mounts to the vehicle frame, an air bag assembly located within the passenger compartment and an inflater assembly to deploy and inflate the air bag. In operation, the air bag is inflated before there is appreciable vehicle--occupant interaction. The air bag is next quickly permitted to deflate, thereby providing a dampered deceleration of the occupant. The air bag must have sufficient capacity to arrest the forward motion of the occupant relative to the vehicle interior without allowing the occupant to penetrate through the air bag and impact the underlying vehicle structure while also having sufficient cushioning to prevent occupant injury directly from the air bag.
While single bag construction remains the predominant approach, inflatable occupant restraint systems incorporating multiple air bags have been previously proposed in the prior art. For example, a typical arrangement having multiple air bags inflates a first air bag to envelope the occupant and a second air bag which functions as a knee bolster is disclosed in U.S. Pat. No. 4,360,223 issued to Kirchoff. Such prior dual bag constructions are directed to systems incorporating multiple air bags designed to independently function.
None of the prior art, however, is without its problems. One problem with traditional inflatable restraint systems involves an inability to adequately protect occupants of a vehicle other than the driver. This problem is inherent in traditional inflatable restraints due to a lack of a flexibility in air bag inflation and deflation rates. The positioning of a driver within a vehicle is relatively predictable. The difficulty in protecting passengers ,other than the driver is the potential of those passengers being "out of position." Passengers other than the driver are not as constrained as to how or where they position themselves within the vehicle. The most significant danger to the "out of position" occupant occurs when they are located in a position forward of a seated position. In such situations, the "out of position" occupant often contacts the air bag while it is still rapidly expanding with tremendous force.
Another problem with traditional inflatable restraint systems is an inability to protect vehicle occupants during continued vehicle motion, resulting from collision or other loss of vehicle control such as vehicle roll over. Current systems are designed to employ, or inflate, upon the detection of significant change in forward motion and thereafter almost immediately deflate. As such, traditional inflatable restraint systems are not adapted to function in response to a rolling-type motion. Furthermore, such systems are not adapted to protect vehicle occupants during continuation of transverse, or rolling-type, motion.
Inflatable restraint systems are designed to deploy and inflate during the time interval between the initial sensing of the impact by a crash sensing mechanism and appreciable resulting forward movement of the occupant relative to the vehicle interior. Because this time interval lasts only milliseconds, the air bag must inflate almost instantaneously with a tremendous flow rate of gas. This tremendous flow rate produces what is commonly referred to in the art as a "hard fill". This "hard fill" can be likened to a small explosion that is contained by the internal boundaries of the air bag.
Ideally, the forces produced during inflation are entirely self-contained by the air bag through its full expansion prior to the occupant initiating contact with the air bag. If the occupant is improperly seated, or "out of position", the impact of the explosion may be partially absorbed by the occupant. As a result, the occupant may suffer an injury from the expansion process of the air bag.
The preferred embodiment of the present invention provides an inflatable restraint system in which an air bag for directly contacting the occupant is inflated at a softer than typical fill rate, thereby minimizing injury resulting from the rapid inflation of the air bag. The preferred embodiment of the inflatable restraint apparatus of the present invention includes an air bag housing and inner and outer air bags securely attached to the air bag housing. The inflatable restraint apparatus further includes a gas generator for generating a gas when activated and a manifold. The manifold is in communication with the gas generator and includes a plurality of discharge ports. At least one of the discharge ports is in communication with the inner air bag. Similarly, at least one of the discharge ports is in communication with the outer air bag.
In a first alternative embodiment, the present invention incorporates multiple inner air bags. A first or main airbag serves to cushion one or more vehicle occupants from forward impact. Second and third inner air bags protect the vehicle occupants from the edges of the vehicle seats or the vehicle doors.
In a second alternative embodiment, the present invention additionally incorporates motion sensing means, including a crash sensor for generating an air bag inflation signal and a triaxial accelerometer for detecting acceleration along each of the three orthogonal axes of direction and generating an air bag deflation signal. The second alternative embodiment further includes a controller operative with the motion sensing means and the actuator for inflating the inner and outer air bags and controlling the rate and/or initiation of deflation of at least one of the air bags. The motion sensing means functions to more fully protect vehicle occupants during situations involving vehicle roll over.